Black Vine Weevil

Otiorhynchus sulcatus

Black Vine Weevil, Snout Beetle , Vine Weevil

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A close up of a black vine weevil
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Vine Weevil is a type of beetle that feeds off of a broad range of plants, both indoors and out. However, it has the most effect on plants that are grown in containers. They can be found in spring and summer eating leaves, but during autumn and winter, the grubs cause the most damage by feeding off the roots, which can cause the plant to wilt and possibly die.
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Traits

Grubs feed off the roots to plants resulting in wilting plant death.
Vine weevil eggs are a source of food for predatory insects.

Appearance

The adult weevil is a dark black, matte colour and have fused wing covers so are unable to fly. They have six legs and two long antennas on their head. They're nocturnal, so they come out at night to feed on the outer parts of leaves. The grubs are white with light brown heads that measure around 10mm in length.

Symptoms

You may see irregular notches in your leaf margins during the summer months. When digging up plants you can find white grubs with light brown heads, and these cause the plants to wilt and die during the autumn and winter months through feeding on plant roots.

Activity

Nocturnal

Personality

Order

Coleoptera

Family

Curculionidae

Metamorphosis

Complete

Distribution

Central Europe, including the UK

Biological treatment

Unfortunately, few treatments can eliminate this pest because they burrow within the roots of host plants. It's important to note that Weevils are nocturnal, so you're not going to catch them in the daytime. If you suspect a possible infestation, or, come to find your garden plants have been attacked but there is no sign of any culprit, you may want to attempt a few evening torch checks. Check on and under the leaves and fruits of plants. It's thought that good housekeeping, such as practising: mulching, re-hilling, field sanitation, crop rotation and using clean planting material, can significantly reduce the severity of an infestation. Pheromone traps can be used to monitor pest populations in the garden. Sticky barriers can also be effective in some cases. Likewise, Diatomaceous earth dusted over leaves and around the bases of plants can kill Weevils. Be careful during application, as this stuff is nasty if inhaled and can be extremely irritable when in contact with the eyes. Nematodes can be used and introduced to the soils of your plants, and you can buy these from some garden centres or online. You can use them in both containers or open ground. By using nematodes such as Steinernema kraussei, you can help to reduce any grubs that are in the soil. These should be applied from August to early September for the best results, as larvae will be smaller in size and not have caused too much damage already.

Chemical treatment

Throughout 2019 and during the start of 2020 the European Commission placed new restrictions on neonicotinoids. Neonicotinoids are active, toxic molecules found in some of the products we treat our plants with. Not all products contain neonicotinoids, but it’s our responsibility to always check for banned active ingredients before applying products to our plants. It is recommended to check your pesticides yearly in regards to their authorisation of use. If you possess an excess of a banned EU product, it’s suggested to contact your local authority for further guidance. Currently, imidacloprid, thiamethoxam and clothianidin are banned for outdoor use in the EU because of the threat they pose to pollinating insects. Thiacloprid will be banned for outdoor use in the EU in April 2020. Currently, acetamiprid is still regulated for outdoor use in the EU. It’s thought these products are most effective against aphids and the Colorado Potato Beetle. In the meantime, there are an array of contact insecticides available for use on the market that is more environmentally friendly than the above products (e.g. Natural pyrethrum/pyrethrins and insecticidal soaps). Again, more persistent products include synthetic insecticides with a contact mode of action (e.g. cypermethrin, phenothrin, lambda-cyhalothrin and deltamethrin). These can still be toxic to some wildlife and a pollutant to water bodies, so please take care to research products and read instructions carefully before using them. Please see our ‘Biological Treatments’ for alternative solutions to plant problems.

Attracts this pest

Ornamental plants and fruit plants, in particular vines, Primula, Rhododendron, Heuchera, Cyclamen and strawberries.
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Knowledge and advice

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